Hey guys, here's my problem: I've just got my motor back together and she pulls pretty hard... unfortunately, I can't get the timing to where it should be on 92 octane gas right now! I know that 10.25 : 1 is pretty high with iron heads, but it should be doable, shouldn't it? Right now, there's still a slight ping at 6 degrees advanced, and, based on my calculations, it would seem that the motor wants to be advanced to around 14 degrees of initial advance. While I recognize that that is not really a possibility, 6 seems a little bit low. It doesn't ping in first or second, and only a little bit in third, but it consistently starts at 2500 RPM in fourth and fifth. My question is this: am I getting too much vacuum advance? Should I be investing in an adjustable vacuum can? It seems like once I get above a certain RPM level - such as when vacuum advance starts to pull back - the pinging eases some. Any help would be appreciated.

 

The timing markers have been known not to be wright. Just because it says 6 does not mean it is at 6. I know my timing mark is wrong, when I checked it, it said it was at like 16 degrees. I set it back some and the car just didn't run the same. I put it back up to 16 and watched the plugs and stuff to make sure I wasn't getting detonation, and I am not. The timing mark was just off.

 

Im willing to bet you have too much vacuum advance before the timing mark on the balancer would be off.

Invest in a dial back timing light. Unplug the vac advance canister, and plug the line to the carb. Set initial timing. (set the dial on the timing light to your initial timing setting and then rotate distributor until line on balancer and 0degree mark line up.)

Rev engine to about 3500 RPM and hold it. Turn **** on light again until marks line up, the setting on the light will now tell you your total MECHANICAL ADVANCE + Initial advance.

Connect vacuum line again and rev engine to 3500 RPM. Again turn **** on timimg light until balancer mark and 0degree mark line up. this number is the total of your MECHANICAL ADVANCE+VACUUM ADVANCE+Initial timing.

On my ride the vaccum advance was adding almost 25 degrees of timing on top of 25 degrees of mechanical, my total timing at 4000 RPM was over 50 degrees = ping city.

To fix the issue I quit running the vacuum advance all together, and only run the mechanical. I set the springs so that I had 32 degrees total timing at about 3200 RPM. The engine held about 10 degrees at idle.

Be sure to check the condition of the mechanical advance mechanism, if it is overly loose it can literlly shake and cause timing variances all over the place. Your timing mark should be still when looking at it under the timing light.

Hope that helps

Bagz